五轴高速加工技术应用分析

通过对不同五轴加工机床结构的分析,指出其各自的特点与适应场合,同时通过分析说明五轴联动与高速加工的内在关系及其优越性,提出了五轴高速加工技术的普及化发展趋势。     

五坐标加工中使用坐标内插法控制刀具轴向研究

在五坐标加工中,刀具轴向的剧烈变化很容易伤到被加工零件的曲面,因此对刀具轴向的控制就变得尤为重要.为了解决这个问题,文章提出一种控制刀具轴向光顺变化的方法,使得刀具轴向对被加工曲面几何的表现不敏感,避免刀具轴向的剧烈变化,从而达到了提高加工精度和效率的目的.最后通过实验验证了本方法在曲面加工精度上的有效性,以及达到避免刀具与零件之间干涉的目的.     

A novel adaptive-feedrate interpolation method for NURBS tool path with drive constraints

Feedrate scheduling is crucial for CNC systems to generate a smooth movement which is able to satisfy increasing requirements on machining quality and efficiency. In this paper, a novel adaptive feedrate interpolation method is proposed for NURBS tool path with drive constraints. The tool path is first expressed in NURBS form, and then the satisfaction conditions of drive constraints are derived according to the kinematic and geometric characteristics of the NURBS tool path. On this base, a proportional adjustment algorithm, which can quantitatively reduce the accelerations and jerks of drive axes at the sensitive regions of feed profile, is proposed to achieve the new positions of violated sampling points. After each adjustment, a curve evolution strategy is used to ensure the feed profile is locally or globally deformed to the target positions with a good smoothness of path curve and the avoidance of re-interpolation. Through the iterative adjustment, a smooth feed profile with limited velocities, accelerations and jerks of drive axes is thus yielded along the entire tool path. Finally, performances of the proposed method are validated by performing both simulations and experiments on two freeform NURBS curves. The results show the effectiveness and reliability of the proposed feedrate interpolation method.     

五轴侧铣加工3D刀具半径补偿研究

为了解决五轴联动侧铣加工3D刀具半径补偿的难题,建立了三维空间刀具半径补偿模型;通过对刀具空间不同位姿的异面法矢的最佳补偿点的求取,避免了空间投影造成的误差,解决了五轴轨迹空间转角的半径补偿问题.论文提出的空间半径补偿算法已集成在五轴联动数控系统中,通过加工实验进行了验证.     

Corner rounding of linear five-axis tool path by dual PH curves blending

The widespread linear five-axis tool path (G01 blocks) is usually described by two trajectories. One trajectory describes the position of the tool tip point, and the other one describes the position of the second point on the tool axis. The inherent disadvantages of linear tool path are tangential and curvature discontinuities at the corners in five-axis tool path, which will result in feedrate fluctuation and decrease due to the kinematic constraints of the machine tools. In this paper, by using a pair of quintic PH curves, a smoothing method is proposed to round the corners. There are two steps involved in our method. Firstly, according to the accuracy requirements of the tool tip contour and tool orientation tolerances, the corner is rounded with a pair of PH curves directly. Then, the control polygon lengths of PH curves are adjusted simply to guarantee the continuous variation of the tool orientation at the junctions between the transition curves and the remainder linear segments. Because the PH curves for corner rounding can be constructed without any iteration, and those two rounded trajectories are synchronized linearly in interpolation, which makes this smoothing method can be applied in a high efficiency way. Its high computational efficiency allows it to be implemented in real-time applications. This method has been integrated into a CNC system with an open architecture to implement on-line linear five-axis tool path smoothing. Simulations and experiments validate its practicability and reliability.     

五轴联动数控加工技术的应用

介绍了多轴联动数控加工中心的结构模型,提出了基于典型的CAD/CAM软件UG的多轴编程、后置处理方法和加工实例,并对某一双摆头五轴联动机床阐述了其各轴的坐标变换关系,开发了后处理系统,为多轴联动加工方案的制定提供了参考.     

自由曲面平头立铣刀五轴数控加工轨迹的计算方法

提出了一种在参数坐标系下自适应步长和行距的计算方法 ,该算法考虑了不同刀具接触点处的曲率差异 ,在满足加工精度和粗糙度的前提下 ,又能有效地提高加工效率。该算法适合加工汽车车身模具等曲率变化大的曲面。文中还给出了刀位计算公式。     

2-5轴刀具轨迹路径仿真模块的研究

介绍了2-5轴刀具轨迹的路径仿真模块的实现，首先讲述路径仿真模块的建模理论，体系结构，模块各组成部分的功能以及仿真模块的工作流程；然后介绍该模块在北京北航海尔软件有限公司自主知识产权的CAD/CAM软件CAXA-ME中的实现方法；最后列举仿真实例，并给出2-5轴刀具轨迹的路径仿真图。     

复杂模具型腔多轴联动数控加工刀具轨迹的优化

提出一种新的刀位轨迹预控优化算法和干涉检验算法,使相邻加工轨迹间的残留高度值都等于允许残留高度值(规定精度),从而达到最大的切削带宽,消除了干涉。实验表明,在保证精度的前提下,轨迹数和轨迹长度明显减少,大大提高了多轴联动数控加工的效率。     

基于 ＵＧ 的五轴数控渐进成形轨迹生成研究

针对金属板材五轴数控渐进成形轨迹生成的需求,研究了基于UG的五轴数控渐进成形轨迹生成方法.为使挤压工具能够按照用户所希望的方向挤压板材,给出了五轴数控渐进成形中基于前倾角和侧倾角的挤压工具姿态定义方法.研究了基于等残留高度的五轴不等层间距等高线轨迹生成方法以及交错运动轨迹生成方法,并给出了五轴数控渐进成形加工轨迹应用实例仿真.     

非单调轴类零件数控加工刀具轨迹分析

本文分析了基于华中I型数控系统的数控车床加工非单调轴类零件的几种编程方法,研究了该类零件的各种数控编程方法的优缺点,提出了该类零件数控编程的合理方案。     

人工神经网络在模具型腔加工走刀方式选择中的应用

建立基于人工神经网络的模具型腔粗加工走刀方式的选择模型,设计了学习样本.采用3层反向传播BP网络模拟模具型腔几何参数与数控加工走刀方式的非线性关系,应用训练好的BP网络为模具型腔选择合理的走刀方式.切削加工表明,应用人工神经网络选择走刀方式可以提高模具型腔的加工效率.     

基于模糊推理自校正控制的直接驱动进给系统稳定性分析

直线电机直接驱动进给系统是实现数控机床进给高速化的主要形式，但加工过程中切削力甚至运动部件质量的变化都是系统的干扰，易引起系统不稳定和定位精度下降。离线模糊推理、在线对控制系统实现自校正的控制方法能提高系统的抗干扰能力，并具有良好的实时性。为了研究系统的稳定性，本文介绍了这种基于模糊推理自校正控制的直接驱动进给系统稳定性分析方法，为同类系统设计提供理论参考。     

5轴CNC机床空间运动学研究

在5轴加工中,为使机床CNC系统能根据刀位点数据实时生成机床运动坐标,必须在CNC系统软件中加入机床运动空间坐标变换算法.文章通过建立各中间坐标系,用齐次矩阵方法详细论述了两种典型5轴数控机床空间运动算法.     

多面体零件五轴定位加工研究

通过实例分析了多面体零件加工的工艺特点，研究了利用MasterCAM软件编写五轴定位加工程序的关键技术和后处理方法，在利用Vericut软件进行模拟加工的基础上，进行了切削试验，证明了多面体零件在五轴机床上加工的优越性。     

Analytical modeling of spindle–tool dynamics on machine tools using Timoshenko beam model and receptance coupling for the prediction of tool point FRF

Regenerative chatter is a well-known machining problem that results in unstable cutting process, poor surface quality and reduced material removal rate. This undesired self-excited vibration problem is one of the main obstacles in utilizing the total capacity of a machine tool in production. In order to obtain a chatter-free process on a machining center, stability diagrams can be used. Numerically or analytically, constructing the stability lobe diagram for a certain spindle–holder–tool combination implies knowing the system dynamics at the tool tip; i.e., the point frequency response function (FRF) that relates the dynamic displacement and force at that point. This study presents an analytical method that uses Timoshenko beam theory for calculating the tool point FRF of a given combination by using the receptance coupling and structural modification methods. The objective of the study is two fold. Firstly, it is aimed to develop a reliable mathematical model to predict tool point FRF in a machining center so that chatter stability analysis can be done, and secondly to make use of this model in studying the effects of individual bearing and contact parameters on tool point FRF so that better approaches can be found in predicting contact parameters from experimental measurements. The model can also be used to study the effects of several spindle, holder and tool parameters on chatter stability. In this paper, the mathematical model, as well as the details of obtaining the system component (spindle, holder and tool) dynamics and coupling them to obtain the tool point FRF are given. The model suggested is verified by comparing the natural frequencies of an example spindle–holder–tool assembly obtained from the model with those obtained from a finite element software.     

直接基于点云数据的刀具轨迹生成

直接基于测量数据来获得刀具轨迹的方法操作简单、计算稳定、加工效率高,适应快速制造的发展趋势。论文利用ATOSII光学扫描系统获取模型点云数据,并对点云数据处理,采取直接对点云数据分层,研究了轮廓数据提取,加工区域识别以及刀具轨迹规划等关键问题。     

四元数法改善复杂曲面5轴加工精度研究

提出一种新的刀具轴向设计方法,通过使用四元数法进行刀具轴向规划,以解决曲面5轴数控加工中刀具轴向过度依赖曲面几何特征,造成刀轴剧烈变化所引起的切削恶化问题.在被加工曲面上可能发生过切的区域,指定刀具轴向,再由指定的轴向,直接计算出其他位置的轴向,并与其他刀具轴向设计方法进行对比.实际应用结果表明:采用该方法可以很好地提高复杂曲面切削精度、效率,避免过切.     

基于动态规划算法的孔群加工路线优化

孔群加工路线优化,对于提高多孔类零件的加工效率和质量具有重要意义。通过数控机床上孔群加工工艺路线的分析,利用动态规划算法,对数控机床孔群加工路线进行了优化计算。最后通过实例验证此优化方法在孔群加工中明显提高了数控加工的效率、降低了加工成本。